Computes the hash value for the specified region of the input byte array and copies the specified region of the input byte array to the specified region of the output byte array. (Inherited from HashAlgorithm.)

Hash functions map binary strings of an arbitrary length to small binary strings of a fixed length. A cryptographic hash function has the property that it is computationally infeasible to find two distinct inputs that hash to the same value. Small changes to the data result in large, unpredictable changes in the hash.

A keyed hash algorithm is a key-dependent, one-way hash function used as a message authentication code. Only someone who knows the key can verify the hash. Keyed hash algorithms provide authenticity without secrecy.

Hash functions are commonly used with digital signatures and for data integrity. The HMACSHA1 class is an example of a keyed hash algorithm.